Inconel X-750
Age-hardenable nickel alloy, for springs and heat
Typical values for the temper in the title
Inconel X-750 is Inconel 600 with titanium, aluminum and niobium added, which form strengthening gamma-prime precipitates on aging. It keeps strength and resistance to creep and stress relaxation from sub-zero temperatures up to about 650 °C.
Its best-known use is springs and fasteners at temperature, and also gas turbine parts, metal seals, nuclear reactor parts and hot-forming tools. It is a historical predecessor of Inconel 718, but harder to weld.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | ≈1200 MPa (aged, typical) | |
| Yield strength Rp0.2 | ≈850 MPa (aged, typical) | |
| Elongation A | ≈20% | |
| Modulus of elasticity E | 214 GPa | |
| Density ρ | 8.28 g/cm³ | |
| Machinability | 25% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Ni nickel | min 70 | matrix |
| Cr chromium | 14.0–17.0 | oxidation resistance |
| Fe iron | 5.0–9.0 | |
| Ti titanium | 2.25–2.75 | gamma prime |
| Al aluminum | 0.40–1.00 | gamma prime |
| Nb+Ta niobium | 0.70–1.20 | strengthening |
| C carbon | max 0.08 |
Ranges per Special Metals and Bibus (N07750). Table properties are typical for the aged condition, and depend on the treatment.
Conditions and heat treatment
X-750 has several heat treatments, by form and use (springs, bolts, hot parts).
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed | soft, for forming and machining | forming and machining |
| Aged | full strength | most uses |
| Cold worked and aged | very high strength | wire springs |
Applications
- Springs at temperature
- Bolts and fasteners at temperature
- Gas turbine parts
- Metal seals
- Reactor parts
Fabrication
Welding
Difficult: like other gamma-prime alloys, crack sensitive in the heat-affected zone. For welded parts Inconel 718 is better.
Machining
Work hardens and wears tools. Sharp carbide tools, continuous feed and low speed, without letting the tool rub in place.
Stress relaxation
Resists stress relaxation at temperature, so it suits hot springs and bolts.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| Inconel 718 | 1240–1380 / 1035–1170 MPa | Good — ERNiCrMo-6 | Inconel 718: stronger and more weldable · material page |
| Inconel 600 | 550-690 / 170-345 MPa | Good | Inconel 600: the base, not hardenable · material page |
| A286 | ≥895 MPa (A453 Gr. 660) / ≥585 MPa (A453 Gr. 660) | Fair — crack sensitive | A286: iron based, cheaper, for lower heat · material page |
Common mistakes
Choosing X-750 for a welded part
It is crack sensitive in welding. Inconel 718 is better.
Expecting strength in the annealed condition
Strength comes only from aging.
Using it above about 650 °C under load
Strength and creep resistance drop.
Equivalents, standards and supply
| DIN | 2.4669 |
|---|---|
| UNS | N07750 |
| Standards | ASTM B637 / AMS 5698 |
| Forms | bar · wire · sheet · forging |
| Producers | Special Metals · VDM |
Learn more
Values are typical and for comparison only. For design, rely on the standard and the mill certificate. Sources: ASTM (B127, B164, B168, B443, B575, B619 and others), Special Metals and Haynes data sheets, and the METAL HUB materials database. Inconel and Monel are trademarks of Special Metals, and Hastelloy of Haynes International.
Updated: October 31, 2026